This invention relates to methods and apparatus for winding wire coils on cores of dynamo-electric machine components such as electric motor stators and alternators.
A stator is the outer body of an electric motor. The stator houses wire coils on an iron core. The core may be formed by stacking laminations that have holes through their centers. An insulator board with terminal posts may be attached to an end of the resulting lamination stack. The core thus formed has a walled body with an external surface and an interior surface.
The interior surface defines a longitudinal bore that extends from a back face to a front face. Further, the interior surface has a number of longitudinal slots or grooves. A pair of adjacent slots defines a stator pole between the slots. The pole extends radially inward into the stator bore and has an elongated shape with longitudinal sides formed by the adjacent slots. A wire coil is wound around the pole by placing wire stretches in the adjacent slots and around ends of the pole.
A coil holder form may be attached to the pole to support portions of the coil upward. The coil holder form may be an extension of the pole and may extend out of the bore to axial ends beyond the front face and/or back face of the walled body to support external portions of the coil upward. The axial ends of the form often have coil retaining wall-like structures to prevent wire coils from spilling over the ends. Hereinafter, the term xe2x80x9cpolexe2x80x9d may be understood to include any attached coil holder form, and the terms xe2x80x9cpolexe2x80x9d and xe2x80x9ccoil holderxe2x80x9d may be used interchangeably.
The wire coils are often wound using automated machinery that includes a movable wire dispenser. The wire dispenser travels back and forth through the stator bore alongside the pole, dispensing wire that is deposited on the pole to form the wire coil. A wire guide or shroud is often attached to the pole during the winding of the wire coil to help guide the wire to its final position in the coil. Locking blades inserted from the exterior surface through the body of the core or other suitable devices may be used to attach the shroud to the pole. The shrouds are especially useful in guiding dispensed wire at the ends of the pole where the wire dispenser rotates to cross over from one side of the pole to the other side.
Starting and ending stretches of wire that form the coil are used as lead wires to pass current through the coil. Loose lead wires can cause the wire coil to unwind. Therefore, after completion of the coil winding, lead wires are terminated and fastened, for example, to terminal posts on the insulator board attached to the lamination stack.
For versatility in stator orientation with respect to sources of current supply, the stator may have insulator boards with terminal posts on either or both the front and back faces. However, the starting stretch is often buried under subsequently wound wire stretches, disadvantageously limiting the direction and amount of wire that is available to reach terminal posts. For example, pulling the buried starting stretch toward the back face to reach terminal posts can disturb the wire coil itself.
Another disadvantage common to current methods of winding wire coils is that the starting wire stretch is in the path of subsequent wire stretches. The physical contact between the starting wire stretch and subsequent stretches as they (the subsequent stretches) are being dispensed can damage wire insulation. Damaged wire insulation may lead to electrical shorts and other reliability problems in stator operation.
It would therefore be desirable to have a starting wire stretch that can be optionally pulled in any direction without disturbing the wire coil. It would also be desirable to be able to position the starting wire stretch so that it does not contact subsequent wire stretches as they are being dispensed.
In view of the foregoing, it is an object of this invention to provide a solution for the problems associated with the positioning of the starting stretch of wire in winding of wire coils.
This and other objects of the invention are accomplished by providing wire winding methods and apparatus that include using a set of loop-forming wire pullers. The apparatus includes a movable wire dispenser that dispenses wire stretches to form a coil on a workpiece, for example, a stator core, and a set of wire pullers that are placed in proximity to the front of the workpiece. The wire pullers have ends that can engage and deflect portions of wire stretches.
At the start of the winding operation, the wire dispenser translates through the bore dispensing a starting stretch of wire extending from the back of the workpiece to the front of the workpiece. The wire dispenser then substantially ceases movement as necessary to hold the starting stretch in a substantially fixed location. With the starting stretch in the substantially fixed location, the end of a first wire puller moves from a position near the pole to a first position away from the pole deflecting a first portion of the starting stretch of wire away from the pole. The end of a second wire puller moves from a position near the pole to another position away from the pole deflecting a second portion of the starting stretch of wire away from the pole. A triangular-shaped loop is thereby formed in the starting stretch adjacent to the pole. Further motion of the wire dispenser across and around the front end of pole positions a leg of the loop over the pole. The loop is thus positioned clear of the paths of subsequent wire stretches dispensed by the wire dispenser.
The loop can be held in position by the wire pullers while subsequent wire stretches are being dispensed to form the coil. Once the winding of the coil is complete, the pullers can be disengaged. The loop can be then pulled taut against the coil without disturbing the coil. The loop may be pulled out in either direction through the bore since it is not buried under the subsequent wire stretches making up the coil.